14 PRINCIPAL FEATURES 



fortress. Kilnscy Crag is a well-known example in Wharfduk' 

 (see the Lithograph). 



Malham Cove and Giggleswick Scar are examples of grand 

 and noble cliffs the former 285 feet high occasioned by the 

 Craven fault, which running nearly E. and W., causes at several 

 points enormous vertical faces of limestone, which are opposed 

 to quite different strata on the south, and, wherever the ground 

 admits of it, are very clear and prominent above them. From 

 under Malham Cove, the Aire issues with a perpetual current. 

 The long range of Giggleswick Scar gives out the feeble source, 

 known as the Ebbing and Flowing Well. 



The Swallow Holes which have been mentioned offer many 

 curious phsenomena. We may see them in action, at the foot of 

 slopes of grit and shale, especially after heavy rains have pro- 

 duced many small rills ; for these are often found running into 

 vertical pits, open, or marked by heath, or choked by earthy 

 materials, and the sides of these pits are smoothed and grooved 

 by the water, always more or less acidulated by the shales and 

 the decaying vegetation of the hills. 



In dry seasons these pits may be inspected to various depths, 

 and may be followed in rings round the mountain slopes, or a 

 little above the upper edge of every limestone bed. The rains 

 and rills thus swallowed up by the dry and fissured and perfo- 

 rated limestones, unite and find their way to underground 

 channels, or caverns, which are nowhere more remarkable than 

 in Yorkshire. 



In some cases these are little else than natural fissures, en- 

 larged by the watery currents; in other cases the ground is 

 ' faulty/ or ' shaken,' or in some way weakened along the line 

 of the caverns, and thus broken it has suffered a greater amount 

 of waste than usual. 



Ingleborough Cave, which has been explored by Mr. Farrer, 

 and preserved from wanton injury, is highly instructive as to the 

 origin of the Craven caverns generally. It is specially rich in 

 illustrations of the varied effects of subterranean currents on its 

 floor; and the endless diversity of sparry stalactites and stalag- 



